The present invention relates generally to methods and apparatus for heat shrinking an envelope of heat shrinkable film into close conformity with a product and more particularly to a method and apparatus using hot air and hot water in combination as the shrinking medium to shrink the film.
It is well known to employ various flexible, heat shrinkable sheet materials for packaging products, including food products. These heat shrinkable materials provide an inexpensive, substantially airtight package which will prevent contamination of the product when properly heat sealed and which will maintain perishable items in a state of freshness for a relatively long period of time. In addition, these films enhance the appearance of the product and conform to the contours of the product due to their transparency and shrinking characteristics respectively. Typically, chicken pieces and other refrigerated meat items are packaged for sale to the public in heat shrinkable wrappers.
Heretofore, these packages were wrapped with heat shrinkable film with the film being caused to shrink in so-called "shrink-tunnels" wherein hot air is applied to the package, causing the film to shrink therearound. However, problems with this method have arisen when packaging cold food products since once the film contacts the cold food, shrinking stops even in the presence of hot moving air. The result is a package which may or may not be sealed properly and which presents an unsightly appearance.
Other methods of heat shrinking film around a product include subjecting the product package to immersion in a water bath or passage through a water curtain. This substantial application of water is enough to overcome the problem of the film ceasing to shrink when contacting the cold food product. However, a relatively large amount of energy is required to initially heat the water and maintain the necessary temperature to provide proper shrink wrapping of a product. It is therefore desirable to provide a heat shrinking apparatus which will more efficiently heat shrink wrappers around cold products.